Extended depth of field intraoral imaging apparatus

Abstract

An apparatus for intraoral imaging has an illumination source that directs light to an object. An imaging apparatus forms an image at an image sensor array from reflected light from the object, the imaging apparatus having an optical stop along an optical axis. A phase modulator is disposed at or near the optical stop. An image processor conditions data from the image sensor array and provides processed image data of the object.

The invention claimed is: 
     
       1. An apparatus for intraoral imaging comprising:
 a) an illumination source including an illumination array and a lens assembly that directs imaging light along an illumination path to an object; 
 b) an imaging apparatus that forms an image at an image sensor array from reflected imaging light from the object, the imaging apparatus having an optical stop along an optical axis, wherein pixels of the image sensor array are mapped to pixels of the illumination array; 
 c) a transparent phase modulator disposed at or near the optical stop to generate a uniform point spread function (PSF) at multiple focal distances and different field positions along the optical axis; and 
 d) an image processor that applies uniform digital restoration filtering based on a PSF characteristic to data at different focus distances from the image sensor array and provides processed image data of the object, 
 wherein the PSF characteristic is an energy distribution of the uniform PSF. 
 
     
     
       2. The apparatus of  claim 1  wherein the image processor provides deblurring of the image data. 
     
     
       3. The apparatus of  claim 1  wherein the optical stop is between an objective lens that directs the reflected light through the optical stop and a second lens that directs light from the optical stop to the image sensor array. 
     
     
       4. The apparatus of  claim 1  further comprising a display for rendering the processed image data, wherein the processed image data corresponds to contour images generated with patterned illumination. 
     
     
       5. The apparatus of  claim 1  wherein the phase modulator is a cubic phase modulator. 
     
     
       6. The apparatus of  claim 1  wherein the phase modulator, from a view along the optical axis, is rectangular or circular in shape. 
     
     
       7. The apparatus of  claim 1  wherein the phase modulator has different phase functions in orthogonal x- and y-directions. 
     
     
       8. The apparatus of  claim 1  wherein the illumination source includes a solid-state light emitter. 
     
     
       9. The apparatus of  claim 1  wherein the image sensor array is a color or monochromatic device, wherein the processed image data corresponds to still images, video images, or 3D surface contours generated using structured light patterns. 
     
     
       10. The apparatus of  claim 1  wherein the illumination source generates patterned illumination for surface contour imaging of the object. 
     
     
       11. The apparatus of  claim 1  wherein the uniform PSF is determined by averaging an actual PSF measured at each of the multiple focal distances. 
     
     
       12. The apparatus of  claim 1  wherein the uniform PSF is based on a transmittance function of the transparent phase modulator. 
     
     
       13. The apparatus of  claim 1  wherein the illumination array and the image sensor array have a prescribed 3D spatial relationship. 
     
     
       14. An apparatus for intraoral imaging comprising:
 a) an illumination source including an illumination array and a lens assembly that directs imaging light along an illumination path to a n object; 
 b) an imaging apparatus that forms an image from reflected imaging light from the object at an image sensor array, the imaging apparatus having an optical stop along an optical axis between an objective lens that directs the reflected light through the optical stop and a second lens that directs light from the optical stop to the image sensor array, wherein pixels of the image sensor array are mapped to pixels of the illumination array; 
 c) a transparent phase modulator disposed at or near the optical stop to generate a uniform point spread function (PSF) at multiple focal distances and different field positions along the optical axis; 
 d) an image processor that is programmed with instructions to apply a uniform digital restoration filter based on a PSF characteristic to data at different focus distances from the image sensor array for deblurring according to phase function characteristics of the phase modulator; and provides processed image data of the object; and 
 e) a display in signal communication with the image processor for rendering the processed image data, 
 wherein the PSF characteristic is an energy distribution of the uniform PSF. 
 
     
     
       15. The apparatus of  claim 14  wherein the phase modulator is a cubic phase plate to increase a depth of focus for the intraoral imaging apparatus. 
     
     
       16. An intraoral imaging method comprising:
 a) directing light along an illumination path to an object from an illumination source including an illumination array and a lens assembly; 
 b) directing reflected light from the object along an optical axis through an objective lens of the lens assembly that directs the reflected light through an optical stop; 
 c) disposing a transparent phase modulator along the optical axis, at or near the optical stop to generate a uniform point spread function (PSF) at multiple focal distances and different field positions along the optical axis; 
 d) forming image data at an image sensor array from the imaged reflected light from the object, wherein pixels of the image sensor array are mapped to pixels of the illumination array; 
 e) applying uniform digital restoration filtering based on a PSF characteristic to the image data at different focus distances for deblurring; and 
 f) rendering the restored image data on a display, 
 wherein the PSF characteristic is an energy distribution of the uniform PSF. 
 
     
     
       17. The method of  claim 16  wherein the optical stop is positioned between the objective lens and a second lens, and where the phase modulator causes the imaging system to have similar point spread functions over a range of object distances. 
     
     
       18. The method of  claim 16  wherein conditioning the data for deblurring comprises digitally filtering the data based on a single point spread function.